Photosynthetic electron transport associated with the oxygen evolution center in green plants will be investigated by kinetic applications of electron spin resonance spectroscopy. The overall objectives of the proposed research include: (a) Characterization of the chemical reactants involved in the transformation of solar energy into oxidative potential for water splitting. (b) Elucidation of the intermediates associated with the manganese-protein complex catalysis of water oxidation. (c) Identify the regulatory properties for ATP formation associated with the oxygen evolution locus of the photosynthetic electron transport chain. These project goals reflect the importance of oxygen evolution for photosynthetic growth of green plants and algae. Carbon fixation into carbohydrate polymers (e.g. starch, cellulose, etc.) requires reductive potential of which the ultimate source of electrons is the water oxidation site. Furthermore, the oxygen evolution complex is one of the most intricate, labile, and enigmatic protein aggregates in biological systems. Hence, long term projects to develop specific herbicides, food crops or "energy" crops viable in arid or extreme environments, or improve the yields of basic agricultural crops are dependent on an in-depth understanding of the molecular mechanism of oxygen evolution. The scientific methodology to be applied in this project includes spectroscopic techniques, oxygen evolution and phosphorylation determinations. This multitechnique approach permits phenomenological analysis as well as chemical intermediate characterization of the oxygen evolution process.